Field of the Invention
The present invention relates to an image forming apparatus including an intermediate transfer member.
Description of the Related Art
Exemplary image forming apparatus include an electrophotographic copying machine (e.g., a digital copying machine), electrophotographic printers (e.g., a color laser beam printer and a color LED printer), a multifunction peripheral (MFP), a facsimile apparatus, and a printing apparatus. Such an image forming apparatus is configured to form an image on a recording medium using an electrophotographic image forming process. An example of an image forming apparatus configured to form a color image is an apparatus including a plurality of image forming portions, an intermediate transfer belt, and a transfer device. The plurality of image forming portions are configured to form toner images on a plurality of photosensitive members. The toner images of a plurality of colors formed on the respective photosensitive members by the plurality of image forming portions are transferred onto the intermediate transfer belt. The transfer device is configured to transfer the toner images on the respective photosensitive members onto a recording medium through the intermediate transfer belt. The transfer device includes a transfer roller and a counter roller as a mechanism configured to transfer the toner images onto the recording medium from the intermediate transfer belt. The intermediate transfer belt is stretched around a plurality of rollers including the counter roller. The transfer roller and the counter roller form a nip portion serving as a secondary transfer portion. The intermediate transfer belt passes through the nip portion. A recording medium passes through the nip portion to allow the toner images on the intermediate transfer belt to be transferred onto the recording medium.
Image forming portions on an upstream side and a downstream side in a movement direction of a surface of the intermediate transfer belt are referred to as a first image forming portion and a second image forming portion, respectively. Each of the image forming portions includes a photosensitive member and is configured to form a toner image on the photosensitive member. The toner image formed on the photosensitive member in each image forming portion is transferred onto the intermediate transfer belt in a primary transfer portion formed between the photosensitive member and the intermediate transfer belt. With respect to a timing of image formation on a recording medium at the first image forming portion, a start timing of image formation on the same recording medium at the second image forming portion is delayed based on a surface speed of the intermediate transfer belt, a distance between the photosensitive members in adjacent primary transfer portions, and a detected color misregistration amount.
However, the surface speed of the intermediate transfer belt may fluctuate when a recording medium enters the secondary transfer portion. As for an image to be transferred onto a recording medium following a recording medium entering the secondary transfer portion, toner images of a plurality of colors cannot be correctly superimposed on each other on the intermediate transfer belt due to fluctuations of the surface speed of the intermediate transfer belt, thus causing color misregistration.